Antenna Radio Waves (2D) | mysimulator.uk

Transmitter

Frequency f 98 MHz

Receiver

Antenna length 0.76 m

Angle from antenna axis θ 90°

Wave propagating — tune the receiver to resonance.

Live Readout

Wavelength λ

3.06 m

λ/4 (ideal)

0.76 m

Length detune

Pattern factor sin²θ

1.00

Receiver signal strength 0%

How it works

A dipole antenna driven by an oscillating current radiates an electromagnetic wave that detaches from the rod and travels outward at the speed of light c. The wave's frequency f and wavelength λ are linked by the universal relation v = f·λ, so v = c gives λ = c/f: raise the frequency and the wavelength shrinks.

A short receiving dipole picks up the most signal when its physical length equals a quarter of the wavelength (λ/4) — the classic "rabbit ears" or car whip antenna length — because that length puts the rod into electrical resonance with the driving frequency. Detune the length away from λ/4 and the received signal falls off sharply.

The transmitter also radiates unevenly in direction: intensity follows sin²θ, where θ is the angle measured from the antenna's own axis. Broadside (θ=90°) gets the full doughnut-shaped lobe of maximum power, while along the antenna's axis (θ near 0° or 180°) almost nothing is radiated — this is why real dipole antennas are mounted broadside to their intended coverage area.

Positive field crest Negative field trough Receiver signal LEDs